In a medium size mixing bowl, whisk together the flour, baking powder, and salt.
In a large mixing bowl, cream together the butter and sugar.
Stir in the ricotta, lemon zest, vanilla and egg until just combined.
Now stir in the dry mixture until a soft cake-like batter forms.
Spoon batter onto a baking sheet lined with parchment paper.
Bake at 350°F for 8-10 minutes.
Remove to a cooling rack and make the glaze while the cookies cool.
For the Glaze:
In a small mixing bowl, whisk together the powdered sugar, lemon juice, and 1 tablespoon milk. If needed, add another tablespoon of milk to get the glaze consistency you want.
Drizzle the glaze over the cooled cookies. Add sprinkles, raw sugar, or a little flaky sea salt to the tops (optional).
Notes
In my tests it didn't make a big difference whether I chilled this dough before baking or not. However, if your cookies spread, then the first thing I would try is chilling the dough before baking.
You can easily double or triple this recipe if you are making for party OR you can freeze cookie dough balls to use later.